This invention relates to fluid control valves for very high temperature service, and more particularly to gate valves that will contain the operating pressure satisfactorily during and after exposure to a fire.
As reflected in the patent and other literature, much effort has been expended in recent years to provide industry, and especially that involved in oil and gas production, with stem operated valves that will withstand the destructive effects of fire or other high temperatures without losing their function of safe, fluid-tight control of high pressure systems. This effort has resulted in a variety of designs for valves with metal-to-metal seals, stem backseating, and fusible elements to prevent backseating during normal operating temperatures yet facilitate it when such temperatures are exceeded. However meritorious these designs might be, each has one or more disadvantages that prevents total satisfaction of the user.